# @turf/union

# union

Takes two or more [polygons](http://geojson.org/geojson-spec.html#polygon) and returns a combined polygon. If the input polygons are not contiguous, this function returns a [MultiPolygon](http://geojson.org/geojson-spec.html#multipolygon) feature.

**Parameters**

-   `A` **...[Feature](http://geojson.org/geojson-spec.html#feature-objects)<[Polygon](http://geojson.org/geojson-spec.html#polygon)>** polygon to combine

**Examples**

```javascript
var poly1 = turf.polygon([[
    [-82.574787, 35.594087],
    [-82.574787, 35.615581],
    [-82.545261, 35.615581],
    [-82.545261, 35.594087],
    [-82.574787, 35.594087]
]], {"fill": "#0f0"});
var poly2 = turf.polygon([[
    [-82.560024, 35.585153],
    [-82.560024, 35.602602],
    [-82.52964, 35.602602],
    [-82.52964, 35.585153],
    [-82.560024, 35.585153]
]], {"fill": "#00f"});

var union = turf.union(poly1, poly2);

//addToMap
var addToMap = [poly1, poly2, union];
```

Returns **[Feature](http://geojson.org/geojson-spec.html#feature-objects)<([Polygon](http://geojson.org/geojson-spec.html#polygon) \| [MultiPolygon](http://geojson.org/geojson-spec.html#multipolygon))>** a combined [Polygon](http://geojson.org/geojson-spec.html#polygon) or [MultiPolygon](http://geojson.org/geojson-spec.html#multipolygon) feature

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---

This module is part of the [Turfjs project](http://turfjs.org/), an open source
module collection dedicated to geographic algorithms. It is maintained in the
[Turfjs/turf](https://github.com/Turfjs/turf) repository, where you can create
PRs and issues.

### Installation

Install this module individually:

```sh
$ npm install @turf/union
```

Or install the Turf module that includes it as a function:

```sh
$ npm install @turf/turf
```